P: Slow UI when using Mac and Custom Display Profile

@ann_chown Yes, because your system problem was fixed..the LR issue still exists for many others.

@ann_chown So, in other words, your problem had most likely nothing to do with the LR issue but was probably something else altogether. A full system reinstal sounds like a system issue not a LR issue. Correlation does not prove causation. The human mind likes to find patterns.

During installation, the update should check whether LR works properly with the existing hardware and software after the update. If this is not the case, the update must abort the installation.

Does this mean that with any major Lightroom update, it will be necessary to completely erase and reinstall our Mac? This is not serious.

What bothers me the most about this story is that it will give arguments to those who claim that the problems are due to old hardware or old systems (you know who I'm talking about...).

Because there are two possibilities: either the new version is given as compatible or it's not. If it is, then let's stop blaming allegedly obsolete hardware and systems.

I've also subsequently upgraded to Big Sur - all fine.

I thought I'd just chip in here in case this helps any of you. I am now (I dread typing these words) problem free!

I have a 2019 27 inch Mac. At the time I was running Catalina.

I started having the problems discussed when the new LR release was launched (beginning of November); my screen froze completely every time I opened LR and then my Mac crashed. At that time Adobe told me to uninstall and reinstall LR, which I did to no avail.  Rick then told me to go to Apple as it was probably a problem there. This I did.

Apple helped me to erase my Mac completely and reinstall it. There were a few hiccups along the way, but when I got hold of a senior member of the Apple support team, things started to improve. I'm not a technical person (! at all!) so please bear with me, but as I remember it, when the Mac operating system was reinstalled, instead of using the Time Machine, it was all done manually to avoid bringing bugs back that may have been there. And from then onwards I haven't had any problems. Sorry to be so vague about the process, but it has worked.

That refers to the post immediately above from celinezug, not this thread. This is the thread that post was merged into. 

Sometimes, it is better to shut up one's mouth taking the risk of appearing dumb, than opening it and leaving no doubt.

You said: I have a MBP16 and latest LR and Big Sure - nothing outdated.

My son has both a MBP16 and a M1 Pro, not only with zero issues but he cannot recreate the ones reported here. His systems are absolutely stock, no special mods to either MacOS or to Lightroom. He also has a Dell 27" 4K monitor and Lightroom runs fine on both the external monitor and the laptop display. 

So what is different between your system and his? Problems like this don't just randomly occur. 

He's boxed up his MBP16 to sell but he still can check things on his M1. As the M1 is using Rosetta, I don't think researching problems on that platform are useful until the native version is released. 

Which existing thread, please?